Founding Frontend Engineer (£120k + Equity) at Mozart AI

This is a job that Jill, our AI Recruiter, is recruiting for on behalf of one of our customers. She will pick the best candidates from Jack's network. The next step is to speak to Jack. Job Title Founding Frontend Engineer Salary £120k + Equity Company Description Mozart AI is a $6M seed-funded startup backed by Balderton Capital building a generative audio workstation that gives artists AI-powered control over stems, instruments, and composition. Job Description As Founding Frontend Engineer at Mozart AI, you will own the entire frontend architecture, managing a complex stack including React, WebGL, and TanStack Start. You’ll tackle extreme performance challenges—like rendering 30k rectangles at 60fps—and build the "backend of the frontend" to ensure a seamless, professional experience for music creators worldwide. Location London, UK Why this role is remarkable Work on a performance-critical generative audio workstation featuring a WebGL renderer running at 60fps and managing 3M lines of React code.Join a high-intensity, $6M seed-funded team backed by Balderton Capital as a founding member with significant equity and technical ownership.Build a generational product that moves beyond basic AI generation into professional DAW features like stems, instruments, and individual note control. What You Will Do Architect and own the "backend of the frontend," including complex state management (Zustand), SSR/CSR strategies, and real-time streaming via WebSockets.Develop and maintain a high-performance design system and testing infrastructure (unit, integration, and e2e) to support rapid, large-scale consumer deployments.Collaborate directly with the CTO to shape the technical direction of the product and integrate sophisticated AI-driven audio features into the UI. The ideal candidate Approximately 5 years of professional frontend experience with deep expertise in TypeScript, React, and modern state management libraries.Proven "Startup DNA" with experience as a founding engineer or early employee at a fast-growing consumer brand with high engineering standards.Ability to thrive in an intense, in-office London environment, working a 6-day week to build a category-defining creative tool. Who are Jack & Jill? Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support. And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate. How does this work? Jack's an AI agent for job searching and career coaching. He works for you.Jill is the AI recruiter working for the company. She recruits from Jack's network.If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives. We never post fake jobs This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network. Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description. We appreciate this can make them look a bit suspect, but there isn't much we can do about it. Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.